U.S. patent number 7,591,854 [Application Number 10/667,763] was granted by the patent office on 2009-09-22 for apparatus, system and method for intraoperative performance analysis during joint arthroplasty.
This patent grant is currently assigned to Depuy Products, Inc.. Invention is credited to Ray C. Wasielewski.
United States Patent |
7,591,854 |
Wasielewski |
September 22, 2009 |
**Please see images for:
( Certificate of Correction ) ** |
Apparatus, system and method for intraoperative performance
analysis during joint arthroplasty
Abstract
An instrumented joint trial has a polymer layer defining a
curved contoured articulating surface. A curved contoured sensor
array is positioned below the polymer layer. Other components of
the joint trial, such as a body with a proximal curved contoured
surface, are positioned below the sensor array. The device can be
made by forming a sheet of the polymer over the curved contoured
surface of the joint trial body and then adhering the sensor array
to one curved contoured surface of the formed polymer. The sensor
array conforms to the shape of the formed polymer layer. The system
includes a mating joint trial. The device may be used by
temporarily attaching the joint trial to a resected portion of bone
and then articulating the joint with the instrumented trial in
place.
Inventors: |
Wasielewski; Ray C.
(Westerville, OH) |
Assignee: |
Depuy Products, Inc. (Warsaw,
IN)
|
Family
ID: |
32033726 |
Appl.
No.: |
10/667,763 |
Filed: |
September 22, 2003 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20040064191 A1 |
Apr 1, 2004 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
60414794 |
Sep 30, 2002 |
|
|
|
|
Current U.S.
Class: |
623/20.14;
623/914; 600/377 |
Current CPC
Class: |
A61F
2/4684 (20130101); A61F 2/4657 (20130101); A61F
2230/0015 (20130101); A61F 2002/4696 (20130101); A61F
2002/4688 (20130101); A61F 2002/4666 (20130101); A61F
2002/30133 (20130101); Y10S 623/914 (20130101); A61F
2/389 (20130101) |
Current International
Class: |
A61F
2/38 (20060101) |
Field of
Search: |
;623/20.14-20.36,914
;600/587,595,377 ;606/88,86,89 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Behrens, Fred M.D., et al, "Bendign Stiffness of Unilateral and
Bilateral Fixator Frames," Clinical Orthopaedics and Related
Research (Sep. 1983), p. 103-110. cited by other .
Markolf, Keith L., Ph.D., et al, "In Vitro Measurement of
Bone-Acrylic Interface Pressure During Femoral Component
Insertion," Clinical Orthopaedics and Related Research (Nov.-Dec.
1976), p. 60-66. cited by other .
English, T.A., et al, "In Vivo Records of Hip Loads Using a Femoral
Implant with Telemetric Output (A Preliminary Report)," Journal
Biomedical Engineering (Apr. 1979), vol. 1 (No. 2), p. 111-115.
cited by other .
Oh, Indong, M.D., et al, "Proximal Strain Distribution in the
Loaded Femur," The Journal of Bone and Joint Surgery (Jan. 1978),
vol. 60A (No. 1), p. 75-85. cited by other .
Takahashi, Toshiaki et al, "Soft Tissue Balancing with Pressure
Distribution During Total Knee Arthroplasty," The Journal of Bone
and Joint Surgery (Mar. 1997), p. 235-239. cited by other .
Davy, D.T., et al, "Telemetric Force Measurements Across the Hip
after Total Arthroplasty," The Journal of Bone and Joint Surgery
(Jan. 1988), vol. 70A (No. 1), p. 45-50. cited by other .
Gupta, Sushi K., M.D., et al, "Use of Piezoelectric Film Sensor for
Monitoring Vascular Grafts," The American Journal of Surgery (Aug.
1990), p. 182-186. cited by other .
McDermott, A.G.P., M.D., et al, "A New Method to Measure
Intraosseous Pressures," Clinical Orthopaedics and Related Research
(Jul. 1986), p. 25-27. cited by other .
Mann, R.W., et al, "Rehabilitation Implications of In Vivo Hip
Pressure Measurements," Proceedings of the Ninth Annual Conference
on Rehabilitation Technology (Jun. 23-26, 1986), Association for
the Advancement of Rehabilitation Technology (Minneapolis,
Minnesota (Copyright 1986)). cited by other .
Hodge, W.A., M.D., et al, "Contact Pressures from an Instrumented
Hip Endoprosthesis," The Journal of Bone and Joint Surgery
Incorporated (Oct. 1989), vol. 71A (No. 9), p. 1378-1386. cited by
other .
Wasielewski, Ray C. "Declaration" unpublished, dated Aug. 22, 2007.
cited by other .
Carlson, Charles E., et al, "A Radio Telemetry Device for
Monitoring Cartilage Surface Pressures in the Human Hip," IEEE
Transactions on Biomedical Engineering (Jul. 1974) vol. BME-21, No.
4. cited by other.
|
Primary Examiner: Philogene; Pedro
Parent Case Text
This application claims the benefit of U.S. Provisional Application
No. 60/414,794, filed Sep. 30, 2002.
Claims
I claim:
1. An instrumented prosthetic knee trial comprising: an
articulating surface; a polymer layer at the articulating surface;
a body having a curved contoured concave surface, the concave
surface being curved in two intersecting planes; and a sensor array
between the polymer layer and the curved contoured surface of the
body, the sensor array having a curved contour including a convex
portion and a concave portion, the convex portion and the concave
portion both being curved in two intersecting planes, the convex
portion contacting and conforming to the shape of at least part of
curved contoured concave surface of the body, the sensor array
being capable of generating a signal in response to pressure; the
polymer layer having a curved contour including a convex surface
and a concave surface, the convex surface contacting and conforming
to the shape of at least part of the concave portion of the sensor
array, the convex surface of the polymer layer overlying
substantially all of the concave surface of the sensor array;
wherein the body, sensor array and polymer layer comprise discrete
components, the sensor array being adhered to at least one of the
convex surface of the polymer layer and the concave surface of the
body.
2. The instrumented prosthetic joint trial of claim 1 including a
tibial tray trial, wherein the body comprises a tibial insert trial
received in the tibial tray trial, said polymer layer and sensor
array being carried on the tibial insert trial.
3. The instrumented prosthetic joint trial of claim 1 wherein the
polymer layer has a thickness of about 1/32 inch.
4. The instrumented prosthetic joint trial of claim 1 wherein the
polymer layer comprises polyethylene.
5. The instrumented prosthetic joint trial of claim 1 wherein the
curved contoured surface of the body includes two concave portions,
the curved contour of the sensor array includes two convex portions
contacting the two concave portions of the body and two concave
portions overlying the two convex portions, and the curved contour
of the polymer layer includes two convex surfaces contacting the
two concave portions of the sensor array and two concave surfaces
overlying the two convex surfaces.
6. The instrumented prosthetic joint trial of claim 1 further
comprising electrical leads connected to the sensor array and
extending beyond the polymer layer.
7. A system for balancing soft tissue intraoperatively during knee
joint arthroplasty comprising: a first joint trial having a curved
convex articulating surface; a second joint trial having a curved
concave articulating surface for receiving the convex articulating
surface of the first joint trial, the curved concave articulating
surface of the second joint trial being curved in two intersecting
planes; the second joint trial including: a polymer layer at the
articulating surface, the polymer layer having a curved concave top
surface and an opposite curved convex surface, the curved concave
top surface and the curved convex opposite surface being curved in
two intersecting planes; a sensor array below the polymer layer and
a body below the sensor array, the body defining the curved concave
surface of the second joint trial, the sensor array having a curved
concave portion contacting and substantially conforming to the
curved convex surface of the polymer layer and a curved convex
portion contacting and substantially conforming to the curved
concave surface of the articulating surface of the body, the sensor
array being capable of generating a signal in response to pressure;
a body below the sensor array, the body having a curved concave
surface adjacent to the sensor array; wherein the sensor array, the
polymer layer and body comprise discrete components; and wherein
the sensor array is adhered to at least one of the curved convex
surface of the polymer layer and the curved concave surface of the
body.
8. The system of claim 7 wherein the first joint trial comprises a
femoral trial and the second joint trial comprises a tibial
trial.
9. The system of claim 7 wherein the polymer layer has a thickness
of about 1/32 inch.
10. The system of claim 7 wherein the polymer layer comprises
polyethylene.
11. The system of claim 7 further comprising electrical signal
carrying lines leading from the sensor array, at least parts of
said electrical signal carrying lines being spaced from the polymer
layer.
12. The system of claim 11 further comprising a computer connected
to the electrical signal carrying lines.
13. The system of claim 12 further comprising a camera operatively
connected to the computer.
14. A method of balancing soft tissue during knee joint
arthroplasty comprising: providing a first joint trial having a
curved convex articular surface; providing a second joint trial
having a curved concave articular surface for receiving the convex
articular surface of the first joint trial, the curved concave
articular surface being curved in two intersecting planes; the
second joint trial including: a protective layer at the
articulating surface, the protective layer have a concave surface
and an opposite convex surface, both the concave surface and the
convex surface being curved in two intersecting planes; a sensor
array below the protective layer, the sensor array having a curved
contour substantially conforming to the curved contour of the
articulating surface of the second joint trial, the curved contour
of the sensor array including a convex surface and an opposite
concave surface, the concave surface of the sensor array being
curved in two intersecting planes and contacting the convex surface
of the protective layer, the convex surface of the protective layer
substantially conforming to and substantially covering the concave
surface of the sensor array, the sensor array being capable of
generating a signal in response to pressure; and a body below the
sensor array, the body defining the curved concave surface of the
second joint trial, the curved concave surface being curved in two
intersecting planes, the convex surface of the sensor array
contacting the curved concave surface of the body, the body and the
protective layer comprising discrete components; the sensor array
being adhered to at least one of the curved convex surface of the
protective layer and the curved concave surface of the body; the
method further comprising: resecting adjacent portions of two
bones; placing the first joint trial on one of the resected bones
and placing the second joint trial on the second resected bone;
flexing the bones about the first and second joint trials so that
the curved convex articular surface of the first joint trial bears
against the concave surface of the protective layer of the second
joint trial.
15. The method of claim 14 wherein the protective layer comprises
polyethylene.
16. The method of claim 14 wherein the protective layer has a
thickness of about 1/32 inch.
17. The method of claim 14 further comprising determining the
contact area on one concave area of the articulating surface of the
second joint trial at a plurality of relative positions of the
first and second joint trials.
18. The method of claim 14 further comprising determining the
distribution of pressure on one concave area of the articulating
surface of the second joint trial at a plurality of relative
positions of the first and second joint trials.
19. The method of claim 14 further comprising measuring forces at
the articulation between the first and second trials.
20. The method of claim 14 further comprising intraoperatively
recording data selected from the group including at least one of
the following: images of the surgical procedure; forces at the
articulation between the first and second trials; and pressure
distribution across at least a portion of the sensor array.
21. The method of claim 14 further comprising releasing soft tissue
around the joint.
22. A method of instructing surgeons in the art of knee joint
arthroplasty comprising: providing a first joint trial having a
curved convex articular surface; providing an instrumented second
joint trial having a curved concave articulating surface for
receiving the convex articulating surface of the first joint trial,
the curved concave articulating surface being curved in two
intersecting planes; the second joint trial including: a protective
layer having a curved concave surface and an opposite convex
surface, both the curved concave surface and the convex surface
being curved in two intersecting planes; a sensor array below the
protective layer, the sensor array having a curved contour
including a convex portion and an opposite concave portion, both
the convex portion and the concave portion being curved in two
intersecting planes, the sensor array being capable of generating a
signal in response to pressure; and a body below the sensor array,
the body defining the curved concave surface receiving the convex
portion of the sensor array, the curved concave surface of the body
being curved in two intersecting planes, the body and the
protective layer comprising discrete components; wherein the sensor
array is sandwiched between the body and the protective layer with
the convex portion of the sensor array contacting and conforming to
the concave surface of the body of the second joint trial and with
the convex surface of the protector contacting, conforming to and
substantially covering the concave portion of the sensor array; and
wherein the sensor array is adhered to at least one of the convex
surface of the protective layer and the concave surface of the
body; the method further comprising: resecting adjacent portions of
two bones; placing the first joint trial on one of the resected
bones and placing the second joint trial on the second resected
bone; flexing the bones about the first and second joint trials so
that portions of the first joint trial bear against contact
portions of the protective layer.
23. The method of claim 22 further comprising providing a computer
to receive signals from the sensor array.
24. The method of claim 23 further comprising providing an image
recording device operatively connected to the computer.
25. A system for balancing soft tissue intraoperatively during knee
joint arthroplasty comprising: a body having a curved concave
surface, the curved concave surface being curved in two
intersecting planes; a conformable sensor array; and a preformed
protective cover having a curved concave surface and an opposite
curved convex surface, both the curved concave surface and the
curved convex surface being curved in two intersecting planes, the
convex surface of the preformed protective cover being sized and
shaped to correspond to the shape of the curved concave surface of
the body; wherein the body, the sensor array and preformed
protective cover comprise discrete components; and wherein the
sensor array is adhered to at least one of the body and the
protective cover.
26. The system of claim 25 wherein the preformed protective layer
is locked to the joint trial and the conformable sensor array is
positioned between the curved convex surface of the preformed
protective cover and the curved concave surface of the body.
27. The system of claim 26 wherein the protective layer is adhered
to the sensor array and to the body.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus, system and method
for intraoperative performance analysis during joint
arthroplasty.
In total joint replacement or arthroplasty, bone orientation,
selection of prosthetic joint components and soft tissue balancing
are critical to the success of the procedure. Considering, for
example, total knee arthroplasty, one or more cutting jigs are used
to ensure that the distal end of the femur and proximal end of the
tibia are cut in an orientation that will properly align the
patient's bones. After the bones are cut or resected, prosthetic
components are fixed to the femur, tibia and patella to define the
prosthetic knee joint.
A successful joint replacement or arthroplasty procedure results,
in part, from selection of prosthetic joint components that are
dimensioned and positioned to closely approximate or replicate the
geometry and functional characteristics of a natural, healthy
joint. Typically, the component selection process includes a
pre-operative analysis of joint images. A valuable intraoperative
adjunct to image analysis is the temporary fixation of one or more
provisional components to a bone or bones of interest at a stage of
the arthroplasty procedure prior to permanent fixation of the
prosthetic joint. The provisional components are intended to mimic
certain aspects of the permanent prosthetic joint in order for a
surgeon to validate measurements and to test or "try-out" several
different possible component sizes and configurations. Hence,
provisional components are aptly known as "trials."
In total knee arthroplasty, femoral and tibial trials are used to
assist a surgeon in assessing the correct resection and alignment
prior to implantation of the femoral and tibial portions of the
artificial knee. A surgeon uses a tibial tray trial before fixation
of the final implant to determine the tibial implant size, to check
that and correct bone cut and reaming has occurred, to assess
alignment and to ensure correct tibial component thickness prior to
implanting the tibial components. The surgeon uses the femoral
trial for similar purposes.
Successful knee arthroplasty also requires an analysis of the soft
tissue supporting the knee. The knee is held together by a number
of ligaments, muscles and tendons. Generally, the surgeon must
ensure that these ligaments, muscles and tendons will be properly
balanced with the prosthetic elements in place. A properly balanced
knee joint will demonstrate balanced ligament tension in both
extension and flexion. If the ligaments and tendons around the knee
are not properly balanced, the result may be poor performance,
localized high stress on the prosthetic components and undesirable
wear on the prosthetic components.
Commonly, surgeons assess ligament tension through a subjective
process using spacer blocks and mechanical tensioners. If the
surgeon senses that either the medial or lateral side is under
excess tension, the surgeon relieves the excess tension by
releasing a part of either the medial or lateral collateral
ligament. However, the surgeon does not necessarily obtain the
feedback necessary during ligament release to help assess whether
the release is adequate throughout the range of motion; full range
of motion information can only be obtained with the trial in place.
In addition, the surgeon must be careful to avoid over-release of
the collateral ligaments, since the surgeon cannot undo the
release.
In some cases it is preferable to retain the native posterior
cruciate ligment. Some prosthetic knees are designed to be used
with the posterior cruciate ligament in place along with the
prosthetic device. In these procedures, surgeons assess tension in
the posterior cruciate ligament with femoral and tibial trials in
place on the resected surfaces of the femur and tibia. Too much
tension could result in premature wear of the prosthetic
components, and too little tension can make the knee unstable.
Surgeons generally release some of the fibrous attachments between
the posterior cruciate ligament and the tibia until they are
satisfied with the degree of tension in the ligament. The current
intraoperative posterior cruciate ligament release procedure relies
heavily on the surgeon's experience and subjective observations,
rather than on objective intraoperative measurement of ligament
tension.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides an instrumented
prosthetic knee trial comprising an articulating surface, a polymer
layer, a body and a sensor array. The polymer layer is located at
the articulating surface. The body has a curved contoured surface.
The sensor array is between the polymer layer and the curved
contoured surface of the body. The sensor array has a curved
contour substantially following the curved contour of at least part
of curved contoured surface of the body. The sensor array is
capable of generating a signal in response to pressure. The polymer
layer has a curved contour substantially following the curved
contour of the sensor array. The polymer layer overlies
substantially all of the sensor array.
In another aspect, the present invention provides a knee joint
tension sensor device comprising a polymer layer and a sensor
array. The sensor array is secured to the polymer layer. The
polymer layer and the sensor array both have a curved contour. The
sensor array is capable of generating a signal in response to
pressure.
In another aspect, the present invention provides a system for
balancing soft tissue intraoperatively during knee joint
arthroplasty. The system includes a first joint trial having a
curved convex articulating surface and a second joint trial having
a curved concave articulating surface for receiving the convex
articulating surface of the first joint trial. The second joint
trial includes a polymer layer at the articulating surface, a
sensor array and a body. The sensor array is below the polymer
layer. The sensor array has a curved convex undersurface contour
substantially following the curved concave contour of the
articulating surface. The sensor array is capable of generating a
signal in response to pressure. The body is below the sensor array,
and has a curved concave surface adjacent to the sensor array.
In another aspect, the present invention provides a method of
making an instrumented prosthetic knee trial. A curved contoured
forming surface is provided, along with a conformable sensor array
and a polymer material. The polymer material is formed over the
curved contoured forming surface so that the polymer material has a
curved contoured surface that substantially mates with the curved
contoured forming surface. The forming can be accomplished by
vacuum forming. The formed polymer material and conformable sensor
array are assembled so that the conformable sensor array is
positioned against the curved contoured surface of the polymer
material. The conformable sensor array conforms substantially to
the curved contoured surface of the polymer material.
In another aspect, the present invention provides a method of
balancing soft tissue during knee joint arthroplasty. A first joint
trial having a curved convex articular surface is provided, along
with an instrumented second joint trial. The instrumented second
joint trial has a curved concave articulating surface for receiving
the convex articulating surface of the first joint trial. The
second joint trial includes a curved concave protective layer at
the articulating surface, a sensor array and a body. The sensor
array is below the protective layer. The sensor array has a curved
concave contour substantially following the curved concave contour
of the articulating surface of the second joint trial, and is
capable of generating a signal in response to pressure. The body is
below the sensor array. The body has a curved concave surface
adjacent to the sensor array. The method further comprises
resecting adjacent portions of two bones, placing the first joint
trial on one of the resected bones and the second joint trial on
the second resected bone. The surgeon then flexes the bones about
the first and second joint trials so that portions of the first
joint trial bear against contact portions of the protective
layer.
In another aspect, the present invention provides a method of
instructing surgeons in the art of knee joint arthroplasty. A first
joint trial having a curved convex articular surface is provided,
along with an instrumented second joint trial. The instrumented
second joint trial has a curved concave articulating surface for
receiving the convex articulating surface of the first joint trial.
The second joint trial includes a curved concave protective layer
at the articulating surface, a sensor array and a body. The sensor
array is below the protective layer. The sensor array has a curved
concave top surface contour substantially following the curved
concave contour of the articulating surface of the second joint
trial, and is capable of generating a signal in response to
pressure. The body is below the sensor array. The body has a curved
concave top surface adjacent to the sensor array. The method
further comprises resecting adjacent portions of two bones, placing
the first joint trial on one of the resected bones and the second
joint trial on the second resected bone. The surgeon then flexes
the bones about the first and second joint trials so that portions
of the first joint trial bear against contact portions of the
protective layer allowing for measurement of the forces between the
trials.
In another aspect, the present invention provides a system for
balancing soft tissue intraoperatively during knee joint
arthroplasty. The system comprises a body having a curved concave
surface, a conformable sensor array, and a preformed protective
cover having a curved concave surface and a curved convex
surface.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, prosthetic joint trials are
illustrated, with like reference numbers used for like parts in all
embodiments.
FIG. 1 is a perspective view of an instrumented tibial trial
incorporating the principles of the present invention;
FIG. 2 is a cross-section of the instrumented tibial insert trial
portion of the instrumented tibial trial of FIG. 1, taken along
line 2-2 of FIG. 1;
FIG. 3 is a cross-section of the instrumented tibial insert trial
portion of the instrumented tibial trial of FIGS. 1-2, taken along
line 3-3 of FIG. 1;
FIG. 4 is a diagrammatic view of the instrumented tibial trial of
FIGS. 1-4, together with a femoral trial, in position on the
resected surfaces of a patient;
FIG. 5 is a perspective view of a second embodiment of an
instrumented tibial insert trial;
FIG. 6 is an elevation of the instrumented tibial insert trial of
FIG. 5, shown in partial cross-section;
FIG. 7 is a cross-section of the instrumented tibial insert trial
of FIGS. 5-6, taken along line 7-7 of FIG. 6;
FIG. 8 is a front elevation of a typical femoral trial;
FIG. 9 is a side elevation of the femoral trial of FIG. 8, taken
along line 9-9 of FIG. 8;
FIG. 10 is a front elevation of another typical femoral trial;
FIG. 11 is a side elevation of the femoral trial of FIG. 10, taken
along line 11-11 of FIG. 10;
FIG. 12 is a top plan view of a typical tibial tray trial;
FIG. 13 is a front elevation of the tibial tray trial and stem of
FIG. 12;
FIG. 14 is a diagrammatic view of a system including the
instrumented tibial trial of the present invention, providing input
to a computer that also receives input from an image recorder;
FIG. 15 is a perspective view of a joint tension sensor device
incorporating the principles of the present invention;
FIG. 16 is a cross-section of the joint tension sensor device of
FIG. 15, taken along line 16-16 of FIG. 15;
FIG. 17 is a cross-section of the joint tension sensor device of
FIGS. 15-16, taken along line 17-17 of FIG. 15; and
FIG. 18 is diagrammatic plan view of a sensor mat that can be used
in the present invention, two of which can be joined with a polymer
layer to form the joint tension sensor device of FIGS. 15-17, and
two of which can be joined with a polymer layer and body to form an
instrumented tibial insert trial as illustrated in FIGS. 1-11.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
The first embodiment of the invention, illustrated in FIGS. 1-4,
comprises an instrumented tibial trial insert 10. Another
embodiment of an instrumented tibial trial insert is illustrated in
FIGS. 5-7 at 10A. An embodiment of a joint tension sensor device is
illustrated at 10B in FIGS. 15-17.
Each illustrated tibial trial insert 10, 10A, 10B is part of a
tibial trial that also includes a tibial trial tray and stem, such
as that shown at 11 in FIGS. 12-13. The entire tibial trial
assembly is designated 13 in FIGS. 1 and 4. For a tibial trial
insert like that shown in FIGS. 5-7, the tibial tray and stem would
have a different design than for the design shown in FIGS. 12-13.
Each tibial trial is part of a trial system that also includes a
femoral trial, examples of which are illustrated in FIGS. 8-11 as
12 and 12A. The femoral trials could be one-piece or multiple piece
parts of the system or kit. A surgical kit would typically include
several different sizes of both tibial trials and femoral
trials.
The surgeon uses the trials 11, 12, 12A, 13 (see FIGS. 4, 8-13) as
provisional joint components, removably attaching them to the
resected tibia and femur during the arthroplasty prior to permanent
fixation of the prosthetic joint. It should be understood that
there are a great variety of designs for tibial and femoral trials,
and that the illustrated shapes, sizes and construction (e.g.
modular versus integral) for all the elements are provided by way
of example only; the present invention is not limited to any shape,
size, material, or construction of any element unless expressly set
forth in the claims.
FIG. 4 illustrates two such prosthetic trials 12, 13 in place on a
femur 14 and tibia 16. The trial components 12, 13 are intended to
mimic certain aspects of the permanent prosthetic tibial and
femoral joint elements in order for a surgeon to validate
measurements and to test or "try-out" several different possible
component sizes and configurations.
As shown in FIG. 4, the illustrated instrumented tibial trial 13
includes a distal plate portion 18 for contacting the proximal
plane 20 of the resected tibia 16. The instrumented tibial trial 13
also includes an articulating surface 22, shown in FIGS. 1-3, 5-7
and 15-17. In both embodiments illustrated in FIGS. 1-4 and 5-7,
the articulating surface 22 is part of the instrumented tibial
insert trial 10, 10A. Each articulating surface 22 has a curved
contour with medial and lateral curved concave portions 24, 26
connected by a raised central portion 28 and surrounded by a raised
outer edge 30.
The articulating surface 22 of the instrumented tibial trial 13 is
defined by a polymer layer 32. The polymer layer 32 covers and
protects a sensor array 34. The illustrated sensor array 34 has
medial and lateral curved portions that rest upon complementary
curved concave portions of a body 36. The illustrated sensor array
34 is concave on its proximal surface against the polymer layer 32
and convex on its distal surface against the tibial trial insert
body. In other words, the sensor array 34 is sandwiched between
surfaces of the polymer layer 32 and the body 36 of the tibial
trial insert that have complementary curved contours. The sensor
array is shaped to conform with the shapes of the surfaces above
and below it. These curved contoured portions of the instrumented
tibial trial are shaped to complement the shapes of the condylar
portions at the distal end of the femoral trial, such as the curved
condylar portions shown at 42, 44 in FIGS. 8-11. As shown in FIG.
2, the polymer layer 32 may include side edges 33 that provide an
interference fit over the sides 35 of the body 36.
Generally, the polymer layer 32 should be capable of protecting the
sensor array 34 from the stresses of the trialing process, be
capable of being sterilized for use in surgery, and be capable of
transferring stress to the sensor array 34 so that forces and
pressure distributions and concentrations can be evaluated as
discussed below. The polymer layer 32 in the illustrated
embodiments comprises high density polyethylene. The illustrated
polymer layer has a thickness of about 1/32 inch (about 0.8 mm), or
slightly more, and can be formed from a sheet of polyethylene. A
commercially available material may be used for the polymer layer
32. A suitable example is 0.020'' HDPE sheet and 0.030'' HDPE sheet
material available from Eastech Plastics of Columbus, Ohio. It
should be understood that the particular material and form of this
material are identified for purposes of example only; the present
invention is not limited to any particular polymer or any
particular form of polymer unless expressly called for in the
claims. For example, depending on the procedure used for making the
tibial trial insert, materials such as low density polyethylene and
polypropylene might be usable.
The sensor array 34 in the illustrated embodiments comprises a grid
of pressure transducers, connected together to define a thin,
flexible and conformable sheet. Two sensor arrays 34 could be
provided, one for each of the medial and lateral curved concave
portions 24, 26 of the articulating surface 22. Alternatively, a
single butterfly-shaped sensor array could be provided, one wing
for each of the medial and lateral curved concave portions 24, 26
of the articulating surface 22, as illustrated in FIG. 1. The
pressure transducers produce a signal in response to pressure; in
the illustrated embodiments, the sensor array 34 produces
electrical signals, but the invention is not so limited unless
expressly called for in the claims.
An illustrative sensor array 34 preferably has the following
characteristics: it is thin (e.g 1.5 mm thick), usable over the
range of anticipated pressures (e.g. 5 N/cm.sup.2-200 N/cm.sup.2),
elastically comformable to the insert contour, and has the ability
to be sterilized, particularly by conventional sterilization
techniques. However, it should be understood that unless a
particular characteristic is expressly called for in the claims,
the invention is not intended to be limited to any particular
characteristic.
The sensor array 34 preferably underlies the entire area of the
articulating surface 22 that is designed to interface with the
mating articulating surface of the femoral trial. It should be
understood that the actual shape and dimensions for each sensor
array will therefore vary with the design and size of the
trials.
A suitable example of a commercially available sensor array 34 is
available from novelElectronics Inc. of St. Paul Minn. (and novel
gmbH of Munich, Germany, www.novel.de). It is identified by novel
as part of the "pliance" system. Each pad has 128 pressure sensors,
a thickness of about 1.5 mm, a total sensor area of 43.times.21.5
mm.sup.2, an elasticity of greater than 2%, a sensitivity of less
than 2 N/cm.sup.2 and greater than 4 N/cm.sup.2, and a usable
pressure range of 5-200 N/cm.sup.2. Two such pads may be used in
each instrumented tibial trial insert 10, 10A, 10B. It should be
understood that this particular sensor array and the
above-identified characteristics of the sensor array are provided
by way of example only; the present invention is not limited to
this sensor array or these characteristics unless expressly called
for in the claims. For example, it is expected that new materials
and new products will become commercially available that could be
used with the present invention; for example, a capacitive fabric
could be usable.
It should be understood that the accompanying drawings are not
drawn to scale. Typically, the sensor array may have a thickness on
the order of 1.5 mm or less, for example, while the polymer layer
may have a thickness of about 0.8 mm ( 1/32 inch), for example.
A diagrammatic representation of an example of a sensor mat 49 is
shown in FIG. 18. Two such mats would be present in a sensor array
34 for a single tibial trial.
The body 36 of the prosthetic tibial trial may comprise a standard
tibial insert trial, to be used with a standard corresponding tray
trial, e.g. as shown at 11 in FIG. 4. The standard insert trial may
have a standard proximal surface 37 with standard medial and
lateral portions with concavely-curved contours, as shown at 38, 40
in FIGS. 2-3 and 6-7. Opposite the curved contours 38, 40 the
tibial trial inset has a distal portion that is supported on the
tibial tray trial 11. Generally, in prior designs, the proximal
surface 37 of the body 36 would have been the articulating surface
of the tibial trial.
The tibial trial insert body 36 may be made of standard materials,
such as nylon, UHMWPE, acetal copolymer, polyethylene or
polypropylene, for example, and the tray trial 11 may be made of
standard material such as stainless steel. Such standard prosthetic
tibial trial components are available from DePuy Orthopaedics, Inc.
of Warsaw, Ind. under trademarks such as: LCS.RTM., LCS.RTM.
COMPLETE, PFC SIGMA, and PFC SIGMA RP. However, it should be
understood that these commercial products are identified for
purposes of illustration only; the invention is not limited to any
particular product unless expressly called for in the claims.
The designs, shapes, sizes and construction of the trials may vary
from those shown in the embodiments of FIGS. 1-3. Other implant
designs will typically have trials generally corresponding in shape
and size to the implant components. For example, the tibial trial
of the present invention may be shaped for use with cruciate
retaining knees, as well as posterior stabilized prosthetic knees,
either fixed or mobile bearing. Suitable trials for cruciate
retaining prostheses are illustrated in FIGS. 1-4 and 8-9; suitable
trials for posterior balanced knee prostheses are illustrated in
FIGS. 5-7 and 10-11.
In addition, in some instances it may be desirable to produce an
instrumented tibial trial component where the polymer layer 32 and
sensor array 34 are not adhered to the insert body 36. An example
of such an alternative design is illustrated in FIGS. 15-17.
The femoral trials 12, 12A (FIGS. 8-11) may be standard
commercially available products, made of standard materials.
Standard femoral trials are available from DePuy Orthopaedics, Inc.
of Warsaw, Ind. However, it should be understood that these
commercial products are identified for purposes of illustration
only; the invention is not limited to any particular product unless
expressly called for in the claims.
All of the trials may be used with commercial prosthetic implants
available from DePuy Orthopaedics, Inc. of Warsaw, Ind. However, it
should be understood that these commercial products are identified
for purposes of illustration only; the invention is not limited to
any particular product unless expressly called for in the
claims.
A variety of methods may be used to make the illustrated
instrumented tibial trial 11. For example, a sheet of polymer
material such as high density polyethylene can be placed over the
proximal surface 37 of a standard commercially available tibial
trial insert body 36, such as a nylon body, heated and
vacuum-formed over the trial insert body. During the vacuum forming
process, the sheet of polymer material forms over the proximal
surface 37 of the trial insert body 36. After the polymer material
has cooled, the formed polymer layer 32 is removed from the trial
insert body. Excess polymer material may be trimmed away. The
resultant polymer layer or cover has curved concave condylar
portions on the top side (proximal surface) and curved convex
condylar portions on the underside (distal surface).
The proximal surface 37 of the tibial trial insert body 36 can be
prepared to receive the sensor array 34 and polymer layer 32 by
roughening the surface 37 with fine sandpaper. When the proximal
surface 37 has sufficient porosity to form a bond, a silicone
adhesive (e.g. E43 ELASTOSIL available from Wacker-Chemie GmbH of
Germany) is applied to bond the sensor array 34 to the proximal
surface 37 of the tibial trial insert body 36 and to the underside
of the preformed polymer layer 32. Since the sensor array 34 is
formable and flexible, it becomes contoured in this process, to
follow the curved concave contours of the proximal surface 37 of
the tibial trial insert body 36 and the curved convex contours of
the distal surface of the preformed polymer layer 32. When the
composite tibial trial 13 is complete, electrical connectors 50
from the sensor array 34 extend outward beyond the articulating
surface 22 of the trial; the electrical connectors 50 are
positioned to be easily accessible from the anterior side of the
trial during surgery.
The instrumented tibial trial of the present invention may also be
made in separate components. As shown in the embodiment of FIGS.
15-17, the sensor array 34 can be adhered to a polymer 32 but
maintained separate from the body 36 of the trial. The same sensor
array 34 could then be used, for example, with a plurality of
different thicknesses of trial insert bodies 36.
The joint trial is sterilized prior to use in surgery. For the
instrumented tibial trial insert 10, 10A, 10B, the sterilization
process is preferably one that will adequately sterilize the trial
10, 10A, 10B without damaging the sensor array 34, polymer layer
32, body 36 or bonds between these layers. The sterilization
process is preferably one that can be used repeatedly without
damaging or compromising these layers and the bonds between these
layers. One example of a suitable process is the STERRAD.RTM. 100S
Sterilization System, a low temperature sterilization system
available from Advanced Sterilization Products of Irvine, Calif.
The cycle in this commercial system comprises evacuation of the
sterilization chamber to 400 mTorr, automatic injection and
diffusion of 1.8 ml of vaporized H.sub.2O.sub.2 and activation of
low temperature H.sub.2O.sub.2 gas plasma with 400W RF power at 500
mTorr pressure for 17 minutes. During the second half of the cycle,
the above steps are repeated. The sterilization chamber is then
vented to return it to atmospheric pressure. The sterilization
cycle is then complete. This sterilization system has proven to be
effective for repeat sterilization of the prosthetic tibial trial
described above; it has been used for ten sterilization cycles
without compromising the silicone bond or the capacitive properties
of the sensors. However, it is expected that other sterilization
techniques can be employed, and the present invention should not be
interpreted as being limited to a particular sterilization
technique unless expressly called for in the claims.
It should be understood that the above-described manufacturing
process is provided as an example of one possible method for making
the instrumented trial of the present invention. The invention is
not limited to this or to any other process unless expressly called
for in the claims. Other processes may be used. For example, if the
polymer layer is formed over a metal base having a top surface
shaped like the trial body articulating surface 37, other forming
methods can be used, including methods utilizing higher
temperatures.
The use of a separate master for forming the contoured polymer
layer may be particularly desirable in the case of designs where
vacuum forming is difficult or undesirable. For example, in the
case of trials for posterior-stabilized tibial components, it may
be desirable to design a master or process that allows for the
formation of a polymer layer in the desired shape. The use of a
separate master will allow greater flexibility in the choice of
materials and methods for forming the polymer layer. It should also
be understood that the polymer layer could be made in two or more
pieces to protect discrete sensor arrays.
In addition, due to the expense of each sensor array 34, it may be
desirable to produce a single or limited number of independent
joint tension sensor devices, such as that shown at 10B in FIGS.
15-17. Such a joint tension sensor device can be used with more
than one size of tibial trial; for example, such a joint tension
sensor device could be designed to be used with two or three close
sizes of trials.
Moreover, it may be desirable to use separate sensor elements or
arrays that are connected to provide input to the same computer.
The term "sensor array" as used herein should be understood to
include both integral and separate configurations of sensors and
sensor mats unless expressly limited by the claims. "Sensor array"
is intended to broadly encompass devices such as those described
herein as well as those made of other materials (e.g., a capacitive
fabric) and having other characteristics.
In use in arthroplasties, the surgeon performs the initial surgical
steps in a standard manner. When the point of trialing is reached,
the surgeon uses the instrumented joint trial of the present
invention (e.g., tibial trial 13) instead of prior art joint
trials, along with a standard complementary prosthetic joint trial
(e.g. femoral trial 12, 12A). The electrical connector 50 of the
sensor array 34 is hooked up to one end of a lead cord, shown
diagrammatically at 52 in FIG. 14, the other end of which is hooked
up to a computer, shown diagrammatically at 54 in FIG. 14. The lead
cord 52 can be kept sterile in the field by covering it with a
clear tube drape. The system may also include a image recorder,
shown diagrammatically at 56 in FIG. 14, such as a digital video
camera, that is also connected to the computer 54. The computer may
be programmed with commercially available software for analysis of
the data provided by the instrumented tibial trial; suitable
software is available from novel Electronics gmbH under the
designation "pliance" ("pliance FTM-KE" software, along with other
components such as a "pliance FTM-KE" electronics analyzer, other
novel KE software, etc.).
The surgeon then manipulates the patient's leg (or other limb as
the case may be), taking the knee through its full range of motion.
As the surgeon does so, the articulating distal surface of the
femoral trial contacts the articulating proximal surface of the
polymer layer of the tibial trial. Depending on the gap between the
resected femur and tibia and the size of trials used and the
condition of the soft tissue around the joint, there will be forces
between the articulating surfaces of the trials. These forces may
vary in concentration, position and magnitude with, for example,
the position of the knee. The surgeon may concurrently analyze the
pressure distribution in each condyle to ensure that pressure is
not unduly concentrated in one area, to thereby maximize the
longevity of the implant.
From the forces measured and pressure distributions, the surgeon
can also determine whether additional bone must be removed, whether
soft tissue needs to be released, and whether the size of implant
is optimal, for example. A series of small soft tissue releases can
be performed, and the surgeon can analyze the effect of each to
ensure that the release is not excessive. Data from the sensor
array 34 can be recorded simultaneously with video images, so that
the surgeon is not limited to "real time" evaluation, but can also
review the data after manipulating the knee.
The surgeon may wish to use the prosthetic trials of the present
invention in conjunction with standard surgical tensors,
particularly those that measure force mechanically. Thus, the
output from the sensor array 34 can be calibrated to correlate with
the mechanical measurement. The surgeon may also wish to use the
prosthetic trials of the present invention together with spacer
blocks.
The display at the computer 54 may include, for example, a video
image, shown diagrammatically at 58 in FIG. 14, a display of the
magnitude of force, shown diagrammatically at 60 in FIG. 14, and a
display of the concentration of pressure, shown diagrammatically at
62 in FIG. 14. As indicated above, the data can be recorded so that
the surgeon is not limited to real time analysis. It should be
understood that these displays are identified by way of example
only; the present invention is not limited to any particular
display or to the use of a computer with such inputs unless
expressly called for in the claims.
In cruciate retaining procedures, the surgeon can use the
information provided to release the posterior cruciate ligament.
The surgeon can balance the posterior cruciate ligament with the
trials in place, and can assess balance using objective data.
After the surgeon is satisfied with the flexion and extension gaps,
the size and components of the prosthetic implant trial and the
balance of forces exerted by the soft tissue surrounding the joint,
the surgeon can then select the optimal prosthetic implant
components and continue with the surgery in the normal manner.
It will be appreciated that the principles of the present invention
can also be applied to the training of surgeons. For example, the
system and method of the present invention could be used in
learning surgical techniques on cadavers. The system of the present
invention may also prove useful in optimizing the designs of
implants.
Although the illustrated embodiments of the invention are
associated with tibial trials, it should be understood that the
femoral trial could alternatively or additionally be the
instrumented one. In addition, the device and methods of the
present invention could be used on spacer blocks used in the
procedure.
Some variations in the above-described components, system and
methods may be desirable. For example, the thickness of the
prosthetic trial may be adjusted. Instead of the trial body being
dimensioned substantially like the corresponding final implant
component, the trial body can be made slightly thinner, to account
for the thickness of the polymer layer and sensor array. Thus, the
body of the trial can be made 1/32 inch thinner than the implant to
account for the thickness of the polymer layer, and can be made an
additional 1 mm thinner to account for the thickness of the sensor
array; however, it may be desirable for the total insert to be
slightly thicker than the reduction in thickness of the trial to
insure loading of the insert.
Thus, the present invention provides the surgeon with an apparatus,
method, and system for evaluating overall knee balance
intraoperatively. It allows the surgeon to assess balance
throughout the range of motion of the knee, avoiding flexion,
extension and midstance imbalances. It can help the surgeon:
understand the influence of implant orientation and soft tissue
balance on one another; manage severe deformities with proper
releases while avoiding inadvertent over-release; and determine the
proper tension in the posterior cruciate ligament for cruciate
sparing implants required to obtain adequate stability and
kinematics. It can be used to train surgeons to perform these tasks
efficiently.
While only specific embodiments of the invention have been
described and shown, it is apparent that various alternatives and
modifications can be made thereto. Moreover, those skilled in the
art will also recognize that certain additions can be made to these
embodiments. It is, therefore, the intention in the appended claims
to cover all such alternatives, modifications and additions as may
fall within the true scope of the invention.
* * * * *
References